Buck-boost DC-DC converters are traditionally used to provide a regulated power supply output signal, which has an output voltage, to a load using a DC source signal, which is provided by a DC power source, such as a battery. The DC source signal has a DC source voltage. The buck-boost DC-DC converter regulates the output voltage based on a setpoint, which is representative of a desired magnitude of the output voltage. The buck-boost DC-DC converter typically operates in either a boost mode or a buck mode to provide the power supply output signal based on the setpoint and the DC source voltage. When the desired magnitude of the output voltage is less than the DC source voltage, the buck-boost DC-DC converter operates in the buck mode. When the desired magnitude of the output voltage is greater than the DC source voltage, the buck-boost DC-DC converter operates in the boost mode.
One version of a traditional buck-boost DC-DC converter uses either the DC source signal or a power supply sourced signal to provide the regulated power supply output signal. The power supply sourced signal has a power supply sourced voltage, which is greater than the DC source voltage. Therefore, when the desired magnitude of the output voltage is less than the DC source voltage, the buck-boost DC-DC converter uses the DC source signal and operates in the buck mode. When the desired magnitude of the output voltage is greater than the DC source voltage, the buck-boost DC-DC converter uses the power supply sourced signal and operates in the boost mode. One particular challenge for traditional buck-boost DC-DC converters occurs when transitioning between the buck mode and the boost mode, which may occur due to changes in the DC source voltage, the setpoint, or both. Such transitioning may cause momentary variations, or glitches, in the regulated power supply output signal. Such momentary variations may cause unacceptable behavior in the load. As a result, there is a need for a buck-boost DC-DC converter that can provide smooth transitioning between a buck mode and a boost mode without causing glitches.